The Molecular Biology Division consists of a closely knit group of independent investigators, united by a common interest in the structure-function relations of membrane bound enzymes and in electron transport mechanisms. The present application is in support of the individual programs of three responsible investigators and of the core personnel and facilities they share. The present application is for competitive renewal of Program Project HL-16251. The title of the project is changed somewhat to reflect more closely current interests oxidation-reduction mechanisms in membrane bound enzymes and in certain other flavoproteins. The research emphasis of the component projects is as follows: (1) oxidation-reduction mechanisms in flavoproteins, including those of the cardiovascular system, (2) structure-function relations in membrane bound enzymes, (3) new approaches to the structure of enzymes in the inner membrane of heart, electron transport in the cardiac respiratory chain as studied with selective inhibitors, and new types of covalently bound flavins.